Phonological and perceptual components of short-term memory for odors.

Just as a written word can be encoded and retained in memory verbally or visually, an odor might be retained as a verbal description or perceptual (olfactory) code. However, one view holds that olfactory memory in the short term does not exist as a separate perceptual code. This was examined in an experiment in which memory errors could be seen as deriving from the substitution of similar verbal or olfactory codes. The odorants presented for recall were divided into three groups: base odorants (which might be replaced in memory by similar verbal or olfactory representations), verbal foils (stimuli dissimilar to the base stimuli in odor but similar in name), and odor foils (the reverse). The substitution errors made in attempting to recall test odorants were classified as verbal or olfactory. A substantial proportion of the errors were olfactory, but verbal errors also occurred. These results support the presence of short-term perceptual olfactory memory rather than simply verbal encoding of olfactory perceptions.

Spatial frequency discrimination: visual long-term memory or criterion setting?

A long-term sensory memory is believed to account for spatial frequency discrimination when reference and test stimuli are separated by long intervals. We test an alternative proposal: that discrimination is determined by the range of test stimuli, through their entrainment of criterion-setting processes. Experiments 1 and 2 show that the 50% point of the psychometric function is largely determined by the midpoint of the stimulus range, not by the reference stimulus. Experiment 3 shows that discrimination of spatial frequencies is similarly affected by orthogonal contextual stimuli and parallel contextual stimuli and that these effects can be explained by criterion-setting processes. These findings support the hypothesis that discrimination over long intervals is explained by the operation of criterion-setting processes rather than by long-term sensory retention of a neural representation of the stimulus.

Phonological and perceptual components of short-term memory for odors.

Just as a written word can be encoded and retained in memory either verbally or in a visual form, so it might seem that an odor might be retained as either a verbal description/name or as a perceptual (olfactory) code. However, one view has it that olfactory memory in the short term does not exist as a separate perceptual code. This was examined in an experimental paradigm in which errors in memory could be recognized as deriving from the substitution of similar verbal codes or of similar olfactory codes. The set of odorants presented for recall was divided into three groups: (i) base odorants (odorants that might be replaced in memory either by similar verbal or similar olfactory representations); (ii) verbal foils (stimuli dissimilar to the base stimuli in odor but which is similar in name); and (iii) odor foils (the reverse). The substitution errors made when attempting to recall test odorants were classified as verbal errors or olfactory errors. A substantial proportion of the errors were olfactory, but verbal errors also occurred. These results support the presence of short-term perceptual olfactory memory, rather than simply verbal encoding of olfactory perceptions.

A comparison of the encoding of content and order in olfactory memory and in memory for visually presented verbal materials.

The claim that there is no olfactory short-term memory store, as olfactory serial position (SP) effects are absent (Engen, 1987, 1989; Lawless & Engen, 1977), raises the issue whether memory for sensory qualities is differently organized from memories for more cognitive materials in vision and hearing. Early memory processing in olfaction is re-examined by comparing the results of similarly designed experiments which examine short-term memory for words and consonants, and for odours. Memory for content and memory for order were separately examined in each case. Serial position functions were obtained both for visually presented verbal materials and for odours. The serial position effects for content and order memory in both modalities are sufficiently similar in pattern to support the conclusion that short-term memory processing of olfactory and verbal stimuli is conducted by analogous memory mechanisms.

Why Goethe rejected Newton's theory of light.

Observations that he himself had made persuaded Goethe to reject Newton's theory of light and to put forward an alternative theory of the colour phenomena seen with a prism. Duck has argued that Goethe's attack on Newton's theory rested on valid experimental observations that appeared to present a difficulty for Newton's theory but to support his own views on colour. Duck has also proposed that these observations may be accounted for as an instance of the Bezold-Brücke phenomenon. It is argued here that this explanation is invalid and that two other features of colour processing can explain Goethe's observations.

Voice-onset time and tone-onset time: the role of criterion-setting mechanisms in categorical perception.

Problems in modelling categorical perception (CP) and attempts to apply signal detection theory (SDT) to CP are reviewed. An approach based on SDT supplemented by a theory of criterion setting is presented. Criterion setting theory (CST) postulates mechanisms that reset the response criterion on each trial, and it accounts for sequential dependencies. A criterion setting model for discrimination is shown to fit data from the literature. The hypothesis that "sharp" category boundaries may arise from the suppression of noise caused by intertrial dependencies was examined in an experiment on the identification of [ba] and [pa] syllables, and tone combinations of varying tone-onset time. However, it was shown that both positive and negative intertrial dependencies were present. They could be fitted by the criterion-setting model; in this respect, CP resembles standard psychophysical judgements. Examination of the psychometric functions from the two CP tasks shows that they are not normal ogives, as in standard psychophysical tasks: these curves are steeper centrally and flatter at the extremes than a Gaussian ogive; we describe them as "hypersigmoid". The description of CP identification functions as hypersigmoid provides a new, qualitative characterization of the "sharp" category boundaries traditionally claimed for CP. Their causation remains to be determined.

The multiregional and single origin hypotheses of the evolution of modern man: a reconciliation.

A current debate opposes two theories of the origin of modern man. One view is that modern Homo sapiens emerged from Africa relatively recently, most probably within the last two or three hundred thousand years (Wilson & Cann, 1992, Sci. Am. 266(4), 22-27). The opposing view is that modern man has resulted from parallel evolution in different regions, producing convergent modernization of local populations over the last million years or so--the multiregional model (Frayer et al., 1993, Am. Anthrop. 95, 14-50). Proponents of both views believe that their interpretations are irreconcilable. The object of the present paper is to describe a genetic mechanism--mitochondrial exclusion--which offers a basis for a model of human evolution that is compatible with the evidence adduced for both contemporary views. The model proposes a mechanism by which complete replacement of archaic mitochondrial DNA may have occurred in a population produced by recent admixture of archaic and modern types of man.

The internal clock: electroencephalographic evidence for oscillatory processes underlying time perception.

It has been proposed that temporal perception and performance depend on a biological source of temporal information. A model for a temporal oscillator put forward by Treisman, Faulkner, Naish, and Brogan (1990) predicted that if intense sensory pulses (such as auditory clicks) were presented to subjects at suitable rates they would perturb the frequency at which the resulting pattern of interference between sensory pulse rates and time judgments would depend on the frequency of the temporal oscillator and so might allow the frequency to be estimated. Such interference patterns were found using auditory clicks and visual flicker (Treisman & Brogan, 1992; Treisman et al., 1990). The present study examines time estimation together with the simultaneously recorded electroencephalogram to examine whether evidence of such an interference pattern can be found in the EEG. Alternative models for the organization of a temporal system consisting of an oscillator or multiple oscillators are considered and predictions derived from them relating to the EEG. An experiment was run in which time intervals were presented for estimation, auditory clicks being given during those intervals, and the EEG was recorded concurrently. Analyses of the EEG revealed interactions between auditory click rates and certain EEG components which parallel the interference patterns previously found. The overall pattern of EEG results is interpreted as favouring a model for the organization of the temporal system in which sets of click-sensitive oscillators spaced at intervals of about 12.8 Hz contribute to the EEG spectrum. These are taken to represent a series of harmonically spaced distributions of oscillators involved in time-keeping.

Population policy options.

In the review by Kristie Macrakis of Beyond the Wall: Memoirs of an East and West German Spy by Werner Stiller, with Jefferson Adams (editor and translator) [Brassey's (US), McLean, VA, 1992; Maxwell Macmillan, London, UK, 1992] (17 Dec., p. 1908), it is stated that physicist Rolf Dobbertin, who denies any spying, was "sent to Paris in 1956 to study at the expense of the Stasi," was "sentenced to 12 years in prison," and "sat in a French jail for five years before he was released in 1991." Legal documents show that Dobbertin, who was arrested in January 1979 for acts of "communication with agents of a foreign power, dealings that could be harmful [intelligence de nature à nuire] to the military or diplomatic situation of France or to its essential economic interest," was jailed until May 1983. He was subsequently tried in 1990 and sentenced to 12 years in prison, but was acquitted of the above charge by a special Assize Court in a second trial in November 1991. According to Dobbertin, he studied continuously at the University of Rostock from 1952 until 1958, and then taught at the University of Berlin for one year before beginning his work in 1959 at the Centre Nationale de la Recherche Scientifigue in France, where he continues to be employed.

On the relation between time perception and the timing of motor action: evidence for a temporal oscillator controlling the timing of movement.

Studies of time estimation have provided evidence that human time perception is determined by an internal clock containing a temporal oscillator and have also provided estimates of the frequency of this oscillator (Treisman, Faulkner, Naish, & Brogan, 1990; Treisman & Brogan, 1992). These estimates were based on the observation that when the intervals to be estimated are accompanied by auditory clicks that recur at certain critical rates, perturbations in time estimation occur. To test the hypothesis that the mechanisms that underlie the perception of time and those that control the timing of motor performance are similar, analogous experiments were performed on motor timing, with the object of seeing whether evidence for a clock would be obtained and if so whether its properties resemble those of the time perception clock. The prediction was made that perturbations in motor timing would be seen at the same or similar critical auditory click rates. The experiments examined choice reaction time and typing. The results support the hypothesis that a temporal oscillator paces motor performance and that this oscillator is similar to the oscillator underlying time perception. They also provide an estimate of the characteristic frequency of the oscillator.

The internal clock: evidence for a temporal oscillator underlying time perception with some estimates of its characteristic frequency.

Evidence for the proposition that human time perception is determined by an internal clock is largely indirect. It would strengthen the case for this hypothesis if a model for the internal clock were available from which predictions could be derived and tested, and if the basic parameter of such a model, the frequency at which the clock runs, could be estimated. A model for an internal temporal pacemaker is briefly described and its properties are explored by computer simulation. Results are obtained that provide a basis for predicting that, under appropriate conditions, interference between an imposed rhythm and the frequency of a temporal oscillator may cause perturbations in temporal judgment which are related to the characteristic frequency of that oscillator. Experimental data are reported which appear to demonstrate such an interference pattern. These results allow some estimates of the characteristic frequency of the temporal oscillator to be obtained.

A theory of criterion setting: an alternative to the attention band and response ratio hypotheses in magnitude estimation and cross-modality matching.

The attention band and response ratio hypotheses of Green and Luce (1974) and Luce and Green (1974) are discussed and some difficulties are noted. An alternative hypothesis is put forward. This is based on a Thurstonian model for magnitude estimation in which the presented stimulus intensities are subjected to a logarithmic transformation. Response criteria are then applied to the resulting quantities to select corresponding responses. The setting and maintenance of these response criteria are accounted for by a theory of criterion setting previously developed by the senior author (Treisman & Williams, 1984). A similar model is developed for cross-modality matching, and it is shown that these models can predict the V pattern for the coefficient of variation of response ratios, can predict the inverted V pattern for correlations between successive responses, and can account for some of the difficulties found in the literature.

Temporal rhythms and cerebral rhythms.

A model for the internal clock is briefly described. It includes a temporal pacemaker whose rate determines time judgments, and whose frequency is affected by arousal specific to it. Three hypotheses relating time judgments and the alpha rhythm are considered: (a) They may be wholly independent, each reflecting the specific arousal of the mechanism determining it. (b) The alpha rhythm may be an index of a state of general arousal which also acts on the temporal pacemaker. Because of this common influence, the alpha frequency, and the proportion of alpha in the electroencephalogram, may be correlated with the speed of the temporal pacemaker. (c) The same pacemaker may be common to the internal clock and an alpha rhythm generator. Concurrent observations on alpha frequency, alpha prevalence, and temporal productions show that there are no simple relations between these measures such as might support the general arousal or common pacemaker hypotheses. However, relations are found between the variables. More or less regular oscillations occur in their values, some of which are common to two or more of the variables studied. These phenomena are further investigated and described.

Triangles and squares look smaller than they are: some new illusions of extent.

Some new illusions of extent are described, and they are discussed in relation to the Müller-Lyer illusion and the constancy-scaling hypothesis. It is concluded that they support a minimal version of this hypothesis in which certain configurations of lines cause changes in local scale in certain directions, independently of whether or not these configurations are incorporated in larger patterns in a way which supports and receives a depth interpretation.

The cylinder configuration: when is a distortion an illusion?

A figure with one end rounded and the other concluding in an ellipse (the 'cylinder configuration') may appear longer than a rectangle of the same true length. It is proposed that when this configuration is processed as a three-dimensional body, it provides a cue for object orientation which causes the perceptual system to make an adjustment in the direction appropriate for maintaining size constancy. This effect may be considered a normal perceptual adjustment, appropriately applied. When the cylinder configuration is embedded in a context which does not favour its being processed as three-dimensional, a weaker adjustment in length may still occur. It is suggested that this effect, which may properly be classified as an illusion, may arise through direct association of the critical pattern of lines with the process of lengthening produced by the size-constancy mechanisms. Some relations of the present configuration to the Müller-Lyer illusion, and implications for the latter, are also discussed.